In positron emission tomography, the distribution of a radioactive marker substance in the body of a subject being examined is determined, in order in this way to obtain functional images of the biochemical and physiological processes that are taking place. The time resolution that can be achieved in positron emission tomography is rather low compared to other diagnostic methods. The marker substance, also referred to as a radiotracer, requires very different times for reaching different regions of the body, these different times being due to the flow characteristics of the vascular system and to the diffusion properties at the blood-tissue interfaces. In a subsequent analysis of an image from positron emission tomography, it therefore remains unclear which concentration of the marker substance was available at which point in time and at which location.
Therefore, the informativeness of an examination carried out by positron emission tomography is greatly limited. It is possible only with difficulty to differentiate between disturbances which occur in the body of the subject being examined and which result in reduced metabolic activity, and disturbances which are themselves caused by reduced transport of substances into the tissue, for example deficient perfusion. On the other hand, a differentiation of this kind is of significance for a number of applications, for example in order to answer the question of what the prospects of success are for a revascularization procedure in a patient.